| // Copyright 2012 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef V8_ZONE_H_ |
| #define V8_ZONE_H_ |
| |
| #include <limits> |
| |
| #include "src/allocation.h" |
| #include "src/base/logging.h" |
| #include "src/globals.h" |
| #include "src/hashmap.h" |
| #include "src/list.h" |
| #include "src/splay-tree.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| // Forward declarations. |
| class Segment; |
| |
| |
| // The Zone supports very fast allocation of small chunks of |
| // memory. The chunks cannot be deallocated individually, but instead |
| // the Zone supports deallocating all chunks in one fast |
| // operation. The Zone is used to hold temporary data structures like |
| // the abstract syntax tree, which is deallocated after compilation. |
| // |
| // Note: There is no need to initialize the Zone; the first time an |
| // allocation is attempted, a segment of memory will be requested |
| // through a call to malloc(). |
| // |
| // Note: The implementation is inherently not thread safe. Do not use |
| // from multi-threaded code. |
| class Zone final { |
| public: |
| Zone(); |
| ~Zone(); |
| |
| // Allocate 'size' bytes of memory in the Zone; expands the Zone by |
| // allocating new segments of memory on demand using malloc(). |
| void* New(size_t size); |
| |
| template <typename T> |
| T* NewArray(size_t length) { |
| DCHECK_LT(length, std::numeric_limits<size_t>::max() / sizeof(T)); |
| return static_cast<T*>(New(length * sizeof(T))); |
| } |
| |
| // Deletes all objects and free all memory allocated in the Zone. Keeps one |
| // small (size <= kMaximumKeptSegmentSize) segment around if it finds one. |
| void DeleteAll(); |
| |
| // Deletes the last small segment kept around by DeleteAll(). You |
| // may no longer allocate in the Zone after a call to this method. |
| void DeleteKeptSegment(); |
| |
| // Returns true if more memory has been allocated in zones than |
| // the limit allows. |
| bool excess_allocation() const { |
| return segment_bytes_allocated_ > kExcessLimit; |
| } |
| |
| size_t allocation_size() const { return allocation_size_; } |
| |
| private: |
| // All pointers returned from New() have this alignment. In addition, if the |
| // object being allocated has a size that is divisible by 8 then its alignment |
| // will be 8. ASan requires 8-byte alignment. |
| #ifdef V8_USE_ADDRESS_SANITIZER |
| static const size_t kAlignment = 8; |
| STATIC_ASSERT(kPointerSize <= 8); |
| #else |
| static const size_t kAlignment = kPointerSize; |
| #endif |
| |
| // Never allocate segments smaller than this size in bytes. |
| static const size_t kMinimumSegmentSize = 8 * KB; |
| |
| // Never allocate segments larger than this size in bytes. |
| static const size_t kMaximumSegmentSize = 1 * MB; |
| |
| // Never keep segments larger than this size in bytes around. |
| static const size_t kMaximumKeptSegmentSize = 64 * KB; |
| |
| // Report zone excess when allocation exceeds this limit. |
| static const size_t kExcessLimit = 256 * MB; |
| |
| // The number of bytes allocated in this zone so far. |
| size_t allocation_size_; |
| |
| // The number of bytes allocated in segments. Note that this number |
| // includes memory allocated from the OS but not yet allocated from |
| // the zone. |
| size_t segment_bytes_allocated_; |
| |
| // Expand the Zone to hold at least 'size' more bytes and allocate |
| // the bytes. Returns the address of the newly allocated chunk of |
| // memory in the Zone. Should only be called if there isn't enough |
| // room in the Zone already. |
| Address NewExpand(size_t size); |
| |
| // Creates a new segment, sets it size, and pushes it to the front |
| // of the segment chain. Returns the new segment. |
| inline Segment* NewSegment(size_t size); |
| |
| // Deletes the given segment. Does not touch the segment chain. |
| inline void DeleteSegment(Segment* segment, size_t size); |
| |
| // The free region in the current (front) segment is represented as |
| // the half-open interval [position, limit). The 'position' variable |
| // is guaranteed to be aligned as dictated by kAlignment. |
| Address position_; |
| Address limit_; |
| |
| Segment* segment_head_; |
| }; |
| |
| |
| // ZoneObject is an abstraction that helps define classes of objects |
| // allocated in the Zone. Use it as a base class; see ast.h. |
| class ZoneObject { |
| public: |
| // Allocate a new ZoneObject of 'size' bytes in the Zone. |
| void* operator new(size_t size, Zone* zone) { return zone->New(size); } |
| |
| // Ideally, the delete operator should be private instead of |
| // public, but unfortunately the compiler sometimes synthesizes |
| // (unused) destructors for classes derived from ZoneObject, which |
| // require the operator to be visible. MSVC requires the delete |
| // operator to be public. |
| |
| // ZoneObjects should never be deleted individually; use |
| // Zone::DeleteAll() to delete all zone objects in one go. |
| void operator delete(void*, size_t) { UNREACHABLE(); } |
| void operator delete(void* pointer, Zone* zone) { UNREACHABLE(); } |
| }; |
| |
| |
| // The ZoneScope is used to automatically call DeleteAll() on a |
| // Zone when the ZoneScope is destroyed (i.e. goes out of scope) |
| class ZoneScope final { |
| public: |
| explicit ZoneScope(Zone* zone) : zone_(zone) { } |
| ~ZoneScope() { zone_->DeleteAll(); } |
| |
| Zone* zone() const { return zone_; } |
| |
| private: |
| Zone* zone_; |
| }; |
| |
| |
| // The ZoneAllocationPolicy is used to specialize generic data |
| // structures to allocate themselves and their elements in the Zone. |
| class ZoneAllocationPolicy final { |
| public: |
| explicit ZoneAllocationPolicy(Zone* zone) : zone_(zone) { } |
| void* New(size_t size) { return zone()->New(size); } |
| static void Delete(void* pointer) {} |
| Zone* zone() const { return zone_; } |
| |
| private: |
| Zone* zone_; |
| }; |
| |
| |
| // ZoneLists are growable lists with constant-time access to the |
| // elements. The list itself and all its elements are allocated in the |
| // Zone. ZoneLists cannot be deleted individually; you can delete all |
| // objects in the Zone by calling Zone::DeleteAll(). |
| template <typename T> |
| class ZoneList final : public List<T, ZoneAllocationPolicy> { |
| public: |
| // Construct a new ZoneList with the given capacity; the length is |
| // always zero. The capacity must be non-negative. |
| ZoneList(int capacity, Zone* zone) |
| : List<T, ZoneAllocationPolicy>(capacity, ZoneAllocationPolicy(zone)) { } |
| |
| void* operator new(size_t size, Zone* zone) { return zone->New(size); } |
| |
| // Construct a new ZoneList by copying the elements of the given ZoneList. |
| ZoneList(const ZoneList<T>& other, Zone* zone) |
| : List<T, ZoneAllocationPolicy>(other.length(), |
| ZoneAllocationPolicy(zone)) { |
| AddAll(other, zone); |
| } |
| |
| // We add some convenience wrappers so that we can pass in a Zone |
| // instead of a (less convenient) ZoneAllocationPolicy. |
| void Add(const T& element, Zone* zone) { |
| List<T, ZoneAllocationPolicy>::Add(element, ZoneAllocationPolicy(zone)); |
| } |
| void AddAll(const List<T, ZoneAllocationPolicy>& other, Zone* zone) { |
| List<T, ZoneAllocationPolicy>::AddAll(other, ZoneAllocationPolicy(zone)); |
| } |
| void AddAll(const Vector<T>& other, Zone* zone) { |
| List<T, ZoneAllocationPolicy>::AddAll(other, ZoneAllocationPolicy(zone)); |
| } |
| void InsertAt(int index, const T& element, Zone* zone) { |
| List<T, ZoneAllocationPolicy>::InsertAt(index, element, |
| ZoneAllocationPolicy(zone)); |
| } |
| Vector<T> AddBlock(T value, int count, Zone* zone) { |
| return List<T, ZoneAllocationPolicy>::AddBlock(value, count, |
| ZoneAllocationPolicy(zone)); |
| } |
| void Allocate(int length, Zone* zone) { |
| List<T, ZoneAllocationPolicy>::Allocate(length, ZoneAllocationPolicy(zone)); |
| } |
| void Initialize(int capacity, Zone* zone) { |
| List<T, ZoneAllocationPolicy>::Initialize(capacity, |
| ZoneAllocationPolicy(zone)); |
| } |
| |
| void operator delete(void* pointer) { UNREACHABLE(); } |
| void operator delete(void* pointer, Zone* zone) { UNREACHABLE(); } |
| }; |
| |
| |
| // A zone splay tree. The config type parameter encapsulates the |
| // different configurations of a concrete splay tree (see splay-tree.h). |
| // The tree itself and all its elements are allocated in the Zone. |
| template <typename Config> |
| class ZoneSplayTree final : public SplayTree<Config, ZoneAllocationPolicy> { |
| public: |
| explicit ZoneSplayTree(Zone* zone) |
| : SplayTree<Config, ZoneAllocationPolicy>(ZoneAllocationPolicy(zone)) {} |
| ~ZoneSplayTree() { |
| // Reset the root to avoid unneeded iteration over all tree nodes |
| // in the destructor. For a zone-allocated tree, nodes will be |
| // freed by the Zone. |
| SplayTree<Config, ZoneAllocationPolicy>::ResetRoot(); |
| } |
| |
| void* operator new(size_t size, Zone* zone) { return zone->New(size); } |
| |
| void operator delete(void* pointer) { UNREACHABLE(); } |
| void operator delete(void* pointer, Zone* zone) { UNREACHABLE(); } |
| }; |
| |
| |
| typedef TemplateHashMapImpl<ZoneAllocationPolicy> ZoneHashMap; |
| |
| } // namespace internal |
| } // namespace v8 |
| |
| #endif // V8_ZONE_H_ |